Hong Kong needs to make significant investments in its transport infrastructure to deal with a growing economy and competition from rival cities in the region, the HK2030 Study says.

Unveiled by government planners to the legislature yesterday, the study highlights the main forms of infrastructure development to be undertaken: airport, seaport and road and rail.

It refers for the first time to the possible need to build a third runway at Chek Lap Kok airport.

While the airport's Master Plan 2020 said growth in aviation demand could be satisfied by improvements to the existing airport infrastructure, trends identified by the new study point to the two runways being saturated by that time.

'There may be a need for an additional runway and transport infrastructure beyond this time frame. Early discussions are needed on how additional facilities should be provided to tie in with the long-term airport development,' it says.

This vindicates private studies that have long argued for a third runway to deal with smaller aircraft on mainland and regional routes. The Airport Authority has dismissed this proposal because of the prohibitive cost of enlarging the airport's manmade island.

As such, the most likely measure to overcome the lack of capacity will be for the Airport Authority to partner one of the smaller airports in the Pearl River Delta to provide services into the mainland, an idea roundly criticised by local airlines.

The study also suggests three possible sites for container terminal 10 (CT10): southwest Tsing Yi, northwest Lantau and western Tuen Mun. But it leaves the proposal on when and where to build the terminal to the $8 million Master Plan 2020, due from consultants GHK early next year.

Government sources said the decision on the CT10 site was all but finalised. The site in western Tuen Mun never got off the ground because it would require the government to dredge the Tonggu channel, or a route parallel to it, opening the rival ports of Chiwan and Shekou to 24-hour deep-sea traffic.

The south China ports, whose ability to serve the biggest ships is hampered by tidal restrictions, would benefit greatly from dredging the channel, which is why Hong Kong has been hesitant to approve funding for the 7km stretch under its jurisdiction.

The Tsing Yi site is considered attractive for its relatively deep waters and ample waterfront which would allow CT10 to be built in increments. But the cost of relocating Exxon from its oil products terminal on the site could make building at Tsing Yi prohibitive, the government source said.

Master Plan 2020, under government guidance, is expected to lean towards building CT10 at a site near where the proposed Hong Kong-Zhuhai-Macau bridge will terminate on northwest Lantau. From the landing point of the new bridge, road links would connect it to the northwest New Territories and also to Kowloon by Route 10.